This will certainly strain international relations, as happened when it was revealed that the United States is eavesdropping on German Chancellor Angela Merkel's cell phone -- but is anyone really surprised? Spying on foreign governments is what the NSA is supposed to do. Much more problematic, and dangerous, is that the NSA spies on entire populations. It's a mistake to have the same laws and organizations involved with both activities, and it's time we separated the two.

The former is espionage: the traditional mission of the NSA. It's an important military mission, both in peacetime and wartime, and something that's not going to go away. It's targeted. It's focused. Decisions of whom to target are decisions of foreign policy. And secrecy is paramount.

The latter is very different. Terrorists are a different type of enemy; they're individual actors instead of state governments. We know who foreign government officials are and where they're located: in government offices in their home countries, and embassies abroad. Terrorists could be anyone, anywhere in the world. To find them, the NSA has to look for individual bad actors swimming in a sea of innocent people. This is why the NSA turned to broad surveillance of populations, both in the United States and internationally.

Bruce Schneier

If you think about it, this is much more of a law enforcement sort of activity than a military activity. Both involve security, but just as the NSA's traditional focus was governments, the FBI's traditional focus was individuals. Before and after 9/11, both the NSA and the FBI were involved in counterterrorism. The FBI did work in the United States and abroad. After 9/11, the primary mission of counterterrorist surveillance was given to the NSA because it had existing capabilities, but the decision could have gone the other way.

Because the NSA got the mission, both the military norms and the legal framework from the espionage world carried over. Our surveillance efforts against entire populations were kept as secret as our espionage efforts against governments. And we modified our laws accordingly. The 1978 Foreign Intelligence Surveillance Act (FISA) that regulated NSA surveillance required targets to be "agents of a foreign power." When the law was amended in 2008 under the FISA Amendments Act, a target could be any foreigner anywhere.

Government-on-government espionage is as old as governments themselves, and is the proper purview of the military. So let the commander in chief make the determination on whose cell phones to eavesdrop on, and let the NSA carry those orders out.

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Surveillance is a large-scale activity, potentially affecting billions of people, and different rules have to apply -- the rules of the police. Any organization doing such surveillance should apply the police norms of probable cause, due process and oversight to population surveillance activities. It should make its activities much less secret and more transparent. It should be accountable in open courts. This is how we and the rest of the world regain the trust in the actions of the United States.

In January, President Obama gave a speech on the NSA where he said two very important things. He said that the NSA would no longer spy on Angela Merkel's cell phone. And while he didn't extend that courtesy to the other 82 million citizens of Germany, he did say that he would extend some U.S. constitutional protections against warrantless surveillance to the rest of the world.

Separating espionage from surveillance, and putting the latter under a law enforcement regime instead of a military regime, is a step toward achieving that.